Vapor-permeable, substantially water-impermeable multilayer article

ABSTRACT

This disclosure relates to an article that includes a nonwoven substrate and a film supported by the nonwoven substrate. The film can include a first polymer and a polymer that is immiscible with the first polymer. The first polymer can include a polyolefin and the second polymer can include a polycycloolefin, a polymethylpentene, or a copolymer thereof.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 13/530,432 filed Jun. 22, 2012, and which claims priority fromU.S. Provisional Patent Application No. 61/500,694 filed Jun. 24, 2011,and claims the benefit of the its earlier filing date under 35 U.S.C.119(e); each of U.S. patent application Ser. No. 13/530,432 and U.S.Provisional Patent Application No. 61/500,694 are incorporated herein byreference in their entirety.

TECHNICAL FIELD

This disclosure relates to vapor-permeable, substantiallywater-impermeable multilayer articles, as well as related products andmethods.

BACKGROUND

Films that allow passage of gases at moderate to high transmission ratesare often called breathable. The gases most commonly used to demonstratea film's breathability are water vapor (also referred to herein asmoisture vapor or moisture) and oxygen. The moisture vapor transmissiontest and oxygen transmission test measure the mass or volume of a gastransported across the cross-section of a film in a given unit of timeat a defined set of environmental conditions. Breathable films can beclassified either as microporous films or monolithic films (which arenot porous).

A breathable film can be laminated onto a nonwoven substrate to form avapor-permeable, substantially water-impermeable multilayer article. Avapor-permeable, substantially water-impermeable multilayer article canrefer to an article that allows the passage of a gas but substantiallydoes not allow the passage of water.

SUMMARY

This disclosure is based on the unexpected findings that a polyolefinand a relatively large amount of a polymer that is immiscible with thepolyolefin (also referred to hereinafter as “immiscible polymer”) can beblended together to form a microporous breathable film with superiorprocessability without using a compatibilizer. Such an article can besuitable for use as a construction material (e.g., a housewrap or aroofwrap).

In one aspect, this disclosure features an article that includes a film.The film includes first and second polymers. The first polymer includesa polyolefin. The second polymer is immiscible with the first polymerand includes a polycycloolefin, a polymethylpentene, or a copolymerthereof.

In another aspect, this disclosure features an article (e.g., avapor-permeable, substantially water-impermeable multilayer article)that includes a nonwoven substrate and a film supported by the nonwovensubstrate. The film includes first and second polymers. The firstpolymer includes a polyolefin. The second polymer is immiscible with thefirst polymer and includes a polycycloolefin, a polymethylpentene, or acopolymer thereof.

In another aspect, this disclosure features an article that includes anonwoven substrate and a film supported by the nonwoven substrate. Thefilm includes first and second polymers. The first polymer includes apolyolefin. The second polymer includes a polycycloolefin, apolymethylpentene, or a copolymer thereof.

In another aspect, this disclosure features a construction material thatincludes an article described above.

In still another aspect, this disclosure features a method of making anarticle. The method includes forming a nonwoven substrate and a filmsupported by the nonwoven substrate, and stretching the laminate to formthe article. The film includes first and second polymers. The firstpolymer includes a polyolefin. The second polymer is immiscible with thefirst polymer and includes a polycycloolefin, a polymethylpentene, or acopolymer thereof.

Embodiments can include one or more of the following optional features.

The second polymer can include a poly(cycloolefin-co-olefin), such as apoly(norbornene-co-ethylene) or a copolymer formed from ethylene andnorbornene substituted with a substituent (e.g., a hydrocarbon moietysuch as C₁-C₂₀ alkyl).

The film can include at least about 1% by weight of the second polymer.

The first polymer can include a polyethylene or a polypropylene. Thepolyethylene can be selected from the group consisting of low-densitypolyethylene, linear low-density polyethylene, high-densitypolyethylene, and copolymers thereof.

The film can further include an elastomer or a nanoclay.

The film can further include a pore-forming filler (e.g., calciumcarbonate). For example, the film can include from about 30% by weightto about 70% by weight of calcium carbonate.

The film can be substantially uniform in the absence of acompatibilizer.

The nonwoven substrate can include randomly disposed polymeric fibers,at least a portion of the fibers being bonded to one another.

The article can be embossed.

The article can have a moisture vapor transmission rate (MVTR) of atleast about 35 g/m²/day when measured at 23° C. and 50% relativehumidity (RH %).

The construction material can be a housewrap or a roofwrap.

Forming the laminate can include extruding the film onto the nonwovensubstrate.

The laminate can be stretched at an elevated temperature (e.g., at leastabout 30° C.).

The laminate can be stretched in the machine direction or in thecross-machine direction.

The laminate can be stretched by a method selected from the groupconsisting of ring rolling, tentering, embossing, creping, andbutton-breaking.

The method can further include embossing the laminate prior to or afterstretching the laminate.

The method can further include bonding randomly disposed polymericfibers to produce the nonwoven substrate prior to forming the laminate.

Embodiments can provide one or more of the following advantages.

Without wishing to be bound by theory, it is believed that, as theimmiscible polymer has a polymer backbone similar to that of thepolyolefin polymer in the breathable film, a relatively large amount(e.g., at least about 30% by weight) of the immiscible polymer can beblended with the polyolefin polymer to form a microporous breathablefilm that is substantially uniform and has superior processabilitywithout using a compatibilizer, thereby significantly reducing the costfor manufacturing the film. By contrast, when a conventional immisciblepolymer (e.g., a polystyrene) is blended with the polyolefin polymer atthe same concentration level, a uniform film is generally not formedeven in the presence of a compatibilizer.

Other features and advantages will be apparent from the description,drawings, and claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view of a vapor-permeable, substantiallywater-impermeable multilayer article.

FIG. 2 is a scheme illustrating an exemplary extruding process.

FIG. 3 is a scheme illustrating an exemplary ring-rolling apparatus.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

This disclosure relates to, for example, an article (e.g., avapor-permeable, substantially water-impermeable multilayer article)containing a nonwoven substrate and a microporous breathable filmsupported by the nonwoven substrate. The microporous breathable film caninclude a first polymer (e.g., a polyolefin) and a second polymer thatis immiscible with the first polymer (e.g., a polycycloolefin, apolymethylpentene, or a copolymer thereof). The nonwoven substrate canbe formed from polymeric fibers (e.g., fibers made from polyolefins).

FIG. 1 is a cross-sectional view of a vapor-permeable, substantiallywater-impermeable multilayer article 10 containing a microporousbreathable film 12 and a nonwoven substrate 14.

Microporous Breathable Film

Microporous breathable film 12 can include a first polymer and a secondpolymer immiscible with the first polymer.

In some embodiments, the first polymer includes a polyolefin. As usedherein, the term “polyolefin” refers to a homopolymer or a copolymermade from a linear or branched, cyclic or acyclic alkene. Examples ofpolyolefins that can be used in film 12 include polyethylene,polypropylene, polybutene, polypentene, and polymethylpentene. In someembodiments, film 12 can include two or more (e.g., three, four, orfive) different polyolefins.

Exemplary polyethylene suitable for film 12 include low-densitypolyethylene (e.g., having a density from 0.910 g/cm² to 0.925 g/cm²),linear low-density polyethylene (e.g., having a density from 0.910 g/cm²to 0.935 g/cm²), and high-density polyethylene (e.g., having a densityfrom 0.935 g/cm² to 0.970 g/cm²). High-density polyethylene can beproduced by copolymerizing ethylene with one or more C₄ to C₂₀ α-olefinco-monomers. Examples of suitable α-olefin co-monomers include 1-butene,1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene, andcombinations thereof. The high-density polyethylene can include up to 20mole percent of the above-mentioned α-olefin co-monomers. In someembodiments, the polyethylene suitable for use in film 12 can have amelt index in the range of from about 0.1 g/10 min to about 10 g/10 min(e.g., from about 0.5 g/10 min to 5 g/10 min).

Polypropylene can be used in film 12 by itself or in combination withone or more of the polyethylene polymers described above. In the lattercase, polypropylene can be either copolymerized or blended with one ormore polyethylene polymers. Both polyethylene and polypropylene areavailable from commercial sources or can be readily prepared by methodsknown in the art.

The amount of the first polymer in film 12 can vary depending on thedesired applications. For example, the first polymer can be at leastabout 40% (e.g., at least about 45%, at least about 50%, at least about55%, at least about 60%, at least about 65%, at least about 70%, or atleast about 80%) and/or at most about 99% (e.g., at most about 95%, atmost about 90%, at most about 85%, at most about 80%, at most about 75%,or at most about 70%) of the total weight of film 12.

The second polymer can be immiscible with the first polymer. Forexample, the second polymer can form phase separation when blended withthe first polymer. Without wishing to be bound by theory, it is believedthat using two immiscible polymers in film 12 can form pores uponstretching, which impart breathability to film 12 (i.e., allowingpassage of moisture, but not water, through film 12). As such, thesecond polymer can serve as an organic pore-forming agent. In someembodiments, film 12 can include three or more (e.g., four or five)immiscible polymers.

Examples of suitable second polymers include a polycycloolefin, apolymethylpentene, or a copolymer thereof. The monomers that can be usedto prepare polycycloolefin include non-aromatic cyclic hydrocarbonscontaining one or more (e.g., two or three) ring double bonds. Examplesof suitable monomers include dipentene, dicyclopentadiene,alpha-terpinene, gamma-terpinene, limonene, alpha-pinene, 3-carene,norbornene, and norbornadiene. Examples of suitable polycycloolefinsinclude poly(cycloolefin-co-olefin), such aspoly(norbornene-co-ethylene) or a copolymer formed from ethylene andsubstituted norbornene. A commercial example of a polycycloolefinsuitable for use in film 12 is APEL available from Mitsui ChemicalsAmerica, Inc. (Rye Brook, N.Y.). A commercial example of apolymethylpentene suitable for use in film 12 is TPX MX0002 availablefrom Mitsui Chemicals America, Inc. The substituted norbornene caninclude those substituted with C₁-C₂₀ alkyl, C₃-C₂₀ cycloalkyl, or aryl.

The amount of the second polymer in film 12 can vary depending on thefirst polymer used or the intended applications. For example, the secondpolymer can be at least about 1% (e.g., at least about 5%, at leastabout 10%, at least about 15%, at least about 20%, at least about 25%,or at least about 30%) and/or at most about 60% (e.g., at most about50%, at most about 45%, at most about 40%, at most about 35%, at mostabout 30%, at most about 25%, or at most about 20%) of the total weightof film 12.

Without wishing to be bound by theory, it is believed that, as thesecond polymer has a polymer backbone similar to that of the firstpolymer, a relatively large amount (e.g., at least about 5% by weight orat least about 30% by weight) of the second polymer can be blended withthe first polymer to form microporous breathable film 12 that issubstantially uniform and has superior processability even without usinga compatibilizer, thereby significantly reducing the cost formanufacturing the film. By contrast, when a conventional immisciblepolymer (e.g., a polystyrene) is blended with the first polymer (e.g., apolyolefin) at the same concentration level, a uniform film is generallynot formed even in the presence of a compatibilizer.

In some embodiments, film 12 can further include a pore-forming filler(e.g., an inorganic pore-forming filler) to facilitate generation ofpores upon stretching (e.g., by using a ring-rolling process during themanufacture of multilayer article 10).

The pore-forming filler can have a low affinity to and a lowerelasticity than the polyolefin polymer in film 12. In some embodiments,the pore-forming filler can be a rigid material. It can have anon-smooth surface, or have a surface treated to become hydrophobic.

In some embodiments, the pore-forming filler is in the form ofparticles. In such embodiments, the average value of the maximum lineardimension of the filler particles can be at least about 0.5 micron (atleast about 1 micron or at least about 2 microns) and/or at most about 7microns (e.g., at most about 5 microns or at most about 3.5 microns).Without wishing to be bound by theory, it is believed that fillerparticles with a relatively small average value of the maximum lineardimension (e.g., from about 0.75 microns to 2 microns) can provide abetter balance of compoundability and breathability than fillerparticles with a relatively large average value of the maximum lineardimension.

The pore-forming filler in film 12 can be any suitable inorganic ororganic material, or combinations thereof. Examples of the inorganicfillers include calcium carbonate, talc, clay, kaolin, silicadiatomaceous earth, magnesium carbonate, barium carbonate, magnesiumsulfate, barium sulfate, calcium sulfate, aluminum hydroxide, zincoxide, magnesium oxide, calcium oxide, magnesium oxide, titanium oxide,alumina, mica, glass powder, glass beads (hollow or non-hollow), glassfibers, zeolite, silica clay, and combinations thereof. In someembodiments, the pore-forming filler in film 16 includes calciumcarbonate. In some embodiments, the inorganic pore-forming filler can besurface treated to be hydrophobic so that the filler can repel water toreduce agglomeration of the filler. In addition, the pore-forming fillercan include a coating on the surface to improve binding of the filler tothe polyolefin in film 12 while allowing the filler to be pulled awayfrom the polyolefin when film 12 is stretched or oriented (e.g., duringa ring-rolling process). Exemplary coating materials include stearates,such as calcium stearate. Examples of organic fillers that can be usedin film 16 include wood powder, pulp powder, and other cellulose-typepowders. Polymer powders such as TEFLON powder and KEVLAR powder canalso be included as an organic pore-forming filler. The pore-formingfillers described above are either available from commercial sources orcan be readily prepared by methods known in the art.

The amount of the pore-forming filler in film 12 can vary as desired.For example, film 12 can include from at least about 5% (e.g., at leastabout 10%, at least about 15%, or at least about 20%) to at most about30% (e.g., at most about 25%, at most about 20%, or at most about 15%)by weight of the pore-forming filler (e.g., calcium carbonate).

In some embodiments, film 12 can further include a functionalizedpolyolefin (e.g., functionalized polyethylene or polypropylene), such asa polyolefin graft copolymer. Examples of such polyolefin graftcopolymers include polypropylene-g-maleic anhydride and polymers formedby reacting PP-g-MAH with a polyetheramine. In some embodiments, such afunctionalized polyolefin can be used a compatibilizer to minimize thephase separation between the components in film 12 and/or to improveadhesion between film 12 and nonwoven substrate 14. The compatibilizercan be at least about 0.1% (e.g., at least about 0.2%, at least about0.4%, at least about 0.5%, at least about 1%, or at least about 1.5%)and/or at most about 30% (e.g., at most about 25%, at most about 20%, atmost about 15%, at most about 10%, at most about 5%, at most about 4%,at most about 3%, or at most about 2%) of the total weight of film 12.

Optionally, film 12 can include an elastomer (e.g., a thermoplasticolefin elastomer) to improve the elasticity of the film. Examples ofsuitable elastomers include vulcanized natural rubber, ethylene alphaolefin rubber (EPM), ethylene alpha olefin diene monomer rubber (EPDM),styrene-isoprene-styrene (SIS) copolymers, styrene-butadiene-styrene(SBS) copolymers, styrene-ethylene-butylene-styrene (SEBS) copolymers,ethylene-propylene (EP) copolymers, ethylene-vinyl acetate (EVA)copolymers, ethylene-maleic anyhydride (EMA) copolymers,ethylene-acrylic acid (EEA) copolymers, and butyl rubber. A commercialexample of such an elastomer is VERSIFY (i.e., an ethylene-propylenecopolymer) available from Dow (Midland, Mich.). Film 12 can include fromabout 5% (e.g., at least about 6% or at least about 7%) to at most about30% (e.g., at most about 25%, at most about 20%, or at most about 15%)by weight of the elastomer. Without wishing to be bound by theory, it isbelieved that one advantage of using an elastomer in film 12 is thatmultilayer article 10 containing such a film can have both improvedtensile strength (e.g., by at least about 5% or at least about 10%) andimproved elongation (e.g., by at least about 20% or at least about 50%).

Further, film 12 can optionally include a nanoclay (e.g.,montmorillonite nanoclay). Examples of nanoclays have been described in,e.g., Provisional Application No. 61/498,328, entitled “Vapor-permeable,Substantially Water-impermeable Multilayer Article”.

Nonwoven Substrate

Nonwoven substrate 14 can include randomly disposed polymeric fibers, atleast some of the fibers being bonded to one another. As used herein,the term “nonwoven substrate” refers to a substrate containing one ormore layers of fibers that are bonded together, but not in anidentifiable manner as in a knitted or woven material.

Nonwoven substrate 14 can be formed from any suitable polymers.Exemplary polymers that can be used to form nonwoven substrate 14include polyolefins and polyesters. Examples of suitable polyolefinsinclude polyethylene, polypropylene, and copolymers thereof, such asthose in film 12 described above. Examples of suitable polyestersinclude polyethylene terephthalate (PET), polybutylene terephthalate(PBT), polytrimethylene terephthalate (PTT), polyethylene naphthalate(PEN), polyglycolide or polyglycolic acid (PGA), polylactide orpolylactic acid (PLA), polycaprolactone (PCL), polyethylene adipate(PEA), polyhydroxyalkanoate (PHA), and copolymers thereof.

Nonwoven substrate 14 can be formed from single component fibers, i.e.,fibers containing a polymer having a single chemical structure (e.g., apolymer described in the preceding paragraph such as a polyethylene, apolypropylene, or a polyethylene terephthalate). In some embodiments,nonwoven substrate 14 can include single component fibers made frompolymers having the same chemical structure but differentcharacteristics (e.g., molecular weights, molecular weightdistributions, density, or intrinsic viscosities). For example,substrate 14 can include a mixture of a low-density polyethylene and ahigh-density polyethylene. Such fibers are still referred to as singlecomponent fibers in this disclosure.

Nonwoven substrate 14 can also be formed from multicomponent fibers,i.e., fibers containing polymers with different chemical structures(such as two different polymers described above). For example, substrate14 can be formed from a mixture of a polypropylene and a polyethyleneterephthalate. In some embodiments, a multicomponent fiber can have asheath-core configuration (e.g., having a polyethylene terephthalate asthe core and a polypropylene as the sheath). In some embodiments, amulticomponent fiber can include two or more polymer domains in adifferent configuration (e.g., a side-by-side configuration, a pieconfiguration, or an “islands-in-the-sea” configuration).

In some embodiments, the surface of nonwoven substrate 14 can be formedof a polymer having a chemical structure similar to (e.g., the same typeas) or the same as the chemical structure of a polymer in the surface offilm 12. As an example, a polyolefin (e.g., a polyethylene or propylene)is of the same type as and similar to a different polyolefin (e.g., apolyethylene or propylene). Without wishing to be bound by theory, it isbelieved that such two layers can have improved adhesion. For example,when nonwoven substrate 14 is formed from single component fibers, thefibers can be made from a polyolefin, which has a chemical structuresimilar to or the same as a polyolefin that is used to make film 12.When nonwoven substrate 14 is formed of multicomponent fibers (e.g.,having a sheath-core configuration), the polymer (e.g., a polyolefin inthe sheath) in the fibers that contacts film 12 can have a chemicalstructure similar to or the same as the chemical structure of apolyolefin in film 12. Both examples described above can result in amultilayer article with improved adhesion between film 12 and nonwovensubstrate 14.

Nonwoven substrate 14 can be made by methods well known in the art, suchas a spunlacing, spunbonding, meltblowing, carding, air-through bonding,or calendar bonding process.

In some embodiments, nonwoven substrate 14 can be a spunbonded nonwovensubstrate. In such embodiments, nonwoven substrate 14 can include aplurality of random continuous fibers, at least some (e.g., all) ofwhich are bonded (e.g., area bonded or point bonded) with each otherthrough a plurality of intermittent bonds. The term “continuous fiber”mentioned herein refers to a fiber formed in a continuous process and isnot shortened before it is incorporated into a nonwoven substratecontaining the continuous fiber.

As an example, nonwoven substrate 14 containing single component fiberscan be made by using a spunbonding process as follows.

After the polymer for making single component fibers is melted, themolten polymer can be extruded from an extruding device. The moltenpolymer can then be directed into a spinneret with composite spinningorifices and spun through this spinneret to form continuous fibers. Thefibers can subsequently be quenched (e.g., by cool air), attenuatedmechanically or pneumatically (e.g., by a high velocity fluid), andcollected in a random arrangement on a surface of a collector (e.g., amoving substrate such as a moving wire or belt) to form a nonwoven web.In some embodiments, a plurality of spinnerets with different quenchingand attenuating capability can be used to place one or more (e.g., two,three, four, or five) layers of fibers on a collector to form asubstrate containing one or more layers of spunbonded fibers (e.g., anS, SS, or SSS type of substrate). In some embodiments, one or morelayers of meltblown fibers can be inserted between the layers of theabove-described spunbonded fibers to form a substrate containing bothspunbonded and meltblown fibers (e.g., a nSMS, SMMS, or SSMMS type ofsubstrate).

A plurality of intermittent bonds can subsequently be formed between atleast some of the fibers (e.g., all of the fibers) randomly disposed onthe collector to form a unitary, coherent, nonwoven substrate.Intermittent bonds can be formed by a suitable method such as mechanicalneedling, thermal bonding, ultrasonic bonding, or chemical bonding.Bonds can be covalent bonds (e.g., formed by chemical bonding) orphysical attachments (e.g., formed by thermal bonding). In someembodiments, intermittent bonds are formed by thermal bonding. Forexample, bonds can be formed by known thermal bonding techniques, suchas point bonding (e.g., using calender rolls with a point bondingpattern) or area bonding (e.g., using smooth calender rolls without anypattern). Bonds can cover between about 6 and about 40 percent (e.g.,between about 8 and about 30 percent or between about 22 and about 28percent) of the total area of nonwoven substrate 14. Without wishing tobe bound by theory, it is believed that forming bonds in substrate 14within these percentage ranges allows elongation throughout the entirearea of substrate 14 upon stretching while maintaining the strength andintegrity of the substrate.

Optionally, the fibers in nonwoven substrate 14 can be treated with asurface-modifying composition after intermittent bonds are formed.Methods of applying a surface-modifying composition to the fibers havebeen described, for example, in U.S. Provisional Patent Application No.61/294,328.

The nonwoven substrate thus formed can then be used to form multilayerarticle 10 described above. A nonwoven substrate containingmulticomponent fibers can be made in a manner similar to that describedabove. Other examples of methods of making a nonwoven substratecontaining multicomponent fibers have been described in, for example,U.S. Provisional Patent Application No. 61/294,328.

Method of Making Multilayer Article

Multilayer article 10 can be made by the methods known in the art or themethods described herein. For example, multilayer article 10 can be madeby first applying film 12 onto nonwoven substrate 14 to form a laminate.Film 12 can be applied onto nonwoven substrate 14 by extruding (e.g.,cast extrusion) a suitable composition for film 12 (e.g., a compositioncontaining the first and second polymers described above) at an elevatedtemperature to form a film onto nonwoven substrate 14. In someembodiments, the just-mentioned composition can be extruded (e.g., bytubular extrusion or cast extrusion) to form a web, which can be cooled(e.g., by passing through a pair of rollers) to form a precursor film. Alaminate can then be formed by attaching the precursor film to nonwovensubstrate 14 by using, for example, an adhesive (e.g., a spray adhesive,a hot melt adhesive, or a latex based adhesive), thermal bonding,ultra-sonic bonding, or needle punching.

In some embodiments, multilayer article 10 can include multiple (e.g.,two, three, four, or five) films supported by nonwoven substrate 14,wherein at least one of the films is film 12 described above. Theadditional films can be made by one or more of the materials used toprepare film 12 described above or other materials known in the art. Insome embodiments, nonwoven substrate 14 can be disposed between two ofthe multiple films. In some embodiments, all of the films can bedisposed on one side of nonwoven substrate 14.

FIG. 2 is a scheme illustrating an exemplary process for making alaminate described. As shown in FIG. 2, a suitable composition (e.g., acomposition containing the first and second polymers described above)can be fed into an inlet 26 of an extruder hopper 24. The compositioncan then be melted and mixed in a screw extruder 20. The molten mixturecan be discharged from extruder 20 under pressure through a heated line28 to a flat film die 38. Extrusion melt 40 discharging from flat filmdie 38 can be coated on nonwoven substrate 14 from roll 30. The coatedsubstrate can then enter a nip formed between rolls 34 and 36, which canbe maintained at a suitable temperature (e.g., between about 10-120°C.). Passing the coated substrate through the nip formed between cooledrolls 34 and 36 can quench extrusion melt 40 while at the same timecompressing extrusion melt 40 so that it contacts nonwoven substrate 14.In some embodiments, roll 34 can be a smooth rubber roller with alow-stick surface coating while roll 36 can be a metal roll. A texturedembossing roll can be used to replace metal roll 36 if a multilayerarticle with a textured film layer is desired. When extrusion melt 40 iscooled, it forms film 12 laminated onto nonwoven substrate 14. Thelaminate thus formed can then be collected on a collection roll 44. Insome embodiments, the surface of nonwoven substrate 14 can be corona orplasma treated before it is coated with extrusion melt 40 to improve theadhesion between nonwoven substrate 14 and film 12.

The laminate formed above can then be stretched (e.g., incrementallystretched or locally stretched) to form a vapor-permeable, substantiallywater-impermeable multilayer article 10. Without wishing to be bound bytheory, it is believed that stretching the laminate generates poresbetween the first and second polymers in film 12 that allow air ormoisture to pass through. The laminate can be stretched (e.g.,incrementally stretched) in the machine direction (MD) or thecross-machine direction (CD) or both (biaxially) either simultaneouslyor sequentially. As used herein, “machine direction” refers to thedirection of movement of a nonwoven material during its production orprocessing. For example, the length of a nonwoven material can be thedimension in the machine direction. As used herein, “cross-machinedirection” refers to the direction that is essentially perpendicular tothe machine direction defined above. For example, the width of anonwoven material can be the dimension in the cross-machine direction.Examples of incremental stretching methods have been described in, e.g.,U.S. Pat. Nos. 4,116,892 and 6,013,151.

Exemplary stretching methods include ring rolling (in the machinedirection and/or the cross-machine direction), tentering, embossing,creping, and button-breaking. These methods are known in the art, suchas those described in U.S. Pat. No. 6,258,308 and U.S. ProvisionalPatent Application No. 61/294,328.

In some embodiments, the laminate described above can be stretched(e.g., incrementally stretched) at an elevated temperature as long asthe polymers in the laminate maintain a sufficient mechanical strengthat that temperature. The elevated temperature can be at least about 30°C. (e.g., at least about 40° C., at least about 50° C., or at leastabout 60° C.) and/or at most about 100° C. (e.g., at least about 90° C.,at least about 80° C., or at least about 70° C.). Without wishing to bebound by theory, it is believed that stretching the laminate describedabove at an elevated temperature can soften the polymers in film 12 andnonwoven substrate 14, and therefore allow these polymers to bestretched easily. In addition, without wishing to be bound by theory, itis believed that stretching the laminate described above at an elevatedtemperature can increase the MVTR by increasing the number of the pores,rather than the size of the pores (which can reduce the hydrostatic head(i.e., resistance of water) of the multilayer article). As a result, itis believed that stretching the laminate described above at an elevatedtemperature can unexpectedly improve the MVTR of the resultantmultilayer article while still maintaining an appropriate hydrostatichead of the multilayer article.

FIG. 3 illustrates an exemplary ring-rolling apparatus 320 used toincrementally stretch the laminate described above in the cross-machinedirection. Apparatus 320 includes a pair of grooved rolls 322, eachincluding a plurality of grooves 324. The grooves 324 stretch thelaminate described above to form multilayer article 10. In someembodiments, one or both of rolls 322 can be heated to an elevatedtemperature (e.g., between about 30° C. and about 100° C.) by passing ahot liquid through roll 322. The laminate described above can also beincrementally stretched in the machine direction in a similar manner. Itis contemplated that the laminate can also be incrementally stretchedusing variations of the ring-rolling apparatus 320 and/or one or moreother stretching apparatus known in the art.

In some embodiments, the laminate described above can be embossed priorto or after being stretched (e.g., by using a calendering process). Forexample, the laminate can be embossed by passing through a pair ofcalender rolls in which one roll has an embossed surface and the otherroll has a smooth surface. Without wishing to be bound by theory, it isbelieved that an embossed multilayer article can have a large surfacearea, which can facilitate vapor transmission through the multilayerarticle. In some embodiments, at least one (e.g., both) of the calenderrolls is heated, e.g., by circulating a hot oil through the roll.

Properties of Multilayer Article

In some embodiments, multilayer article 10 can have a suitable MVTRbased on its intended uses. As used herein, the MVTR values are measuredaccording to ASTM E96-A. For example, multilayer article 10 can have aMVTR of at least about 35 g/m²/day (e.g., at least about 50 g/m²/day, atleast about 75 g/m²/day, or at least about 100 g/m²/day) and/or at mostabout 140 g/m²/day (e.g., at most about 130 g/m²/day, at most about 120g/m²/day, or at most about 110 g/m²/day) when measured at 23° C. and 5RH %. For instance, the multilayer article 10 can have a MVTR of between70 g/m²/day and 140 g/m²/day.

In some embodiments, multilayer article 10 can have a sufficient tensilestrength in the machine direction and/or the cross-machine direction.The tensile strength is determined by measuring the tensile forcerequired to rupture a sample of a sheet material. The tensile strengthmentioned herein is measured according to ASTM D5034 and is reported inpounds. In some embodiments, multilayer article 10 can have a tensilestrength of at least about 40 pounds (e.g., at least about 50 pounds, atleast about 60 pounds, at least about 70 pounds, or at least about 80pounds) and/or at most about 160 pounds (e.g., at most about 150 pounds,at most about 140 pounds, at most about 130 pounds, or at most about 120pounds) in the machine direction. In some embodiments, multilayerarticle 10 can have a tensile strength of at least about 35 pounds(e.g., at least about 40 pounds, at least about 50 pounds, at leastabout 60 pounds, or at least about 70 pounds) and/or at most about 140pounds (e.g., at most about 130 pounds, at most about 120 pounds, atmost about 110 pounds, or at most about 100 pounds) in the cross-machinedirection.

As a specific example, when multilayer article 10 has a unit weight of1.25 ounce per square yard (osy), it can have a tensile strength of atleast about 40 pounds (e.g., at least about 45 pounds, at least about 50pounds, at least about 55 pounds, or at least about 60 pounds) and/or atmost about 100 pounds (e.g., at most about 95 pounds, at most about 90pounds, at most about 85 pounds, or at most about 80 pounds) in themachine direction, and at least about 35 pounds (e.g., at least about 40pounds, at least about 45 pounds, at least about 50 pounds, or at leastabout 55 pounds) and/or at most about 95 pounds (e.g., at most about 90pounds, at most about 85 pounds, at most about 80 pounds, or at mostabout 75 pounds) in the cross-machine direction.

In some embodiments, multilayer article 10 can have a sufficientelongation in the machine direction and/or the cross-machine direction.Elongation is a measure of the amount that a sample of a sheet materialwill stretch under tension before the sheet breaks. The term“elongation” used herein refers to the difference between the lengthjust prior to breaking and the original sample length, and is expressedas a percentage of the original sample length. The elongation valuesmentioned herein are measured according to ASTM D5034. For example,multilayer article 10 can have an elongation of at least about 5% (e.g.,at least about 10%, at least about 20%, at least about 30%, at leastabout 35%, or at least about 40%) and/or at most about 100% (e.g., atmost 90%, at most about 80%, or at most about 70%) in the machinedirection. As another example, multilayer article 10 can have anelongation of at least about 5% (e.g., at least about 10%, at leastabout 20%, at least about 30%, at least about 35%, or at least about40%) and/or at most about 100% (e.g., at most about 90%, at most about80%, or at most about 70%) in the cross-machine direction.

In some embodiments, multilayer article 10 can have a sufficienthydrostatic head value so as to maintain sufficient waterimpermeability. As used herein, the term “hydrostatic head” refers tothe pressure of a column of water as measured by its height that isrequired to penetrate a given material and is determined according toAATCC 127. For example, multilayer article 10 can have a hydrostatichead of at least about 55 cm (e.g., at least about 60 cm, at least about70 cm, at least about 80 cm, at least about 90 cm, or at least about 100cm) and/or at most about 900 cm (e.g., at most about 800 cm, at mostabout 600 cm, at most about 400 cm, or at most about 200 cm).

Multilayer article 10 can be used in a consumer product with or withoutfurther modifications. Examples of such consumer products includeconstruction materials, such as a housewrap or a roofwrap. Otherexamples include diapers, adult incontinence devices, feminine hygieneproducts, medical and surgical gowns, medical drapes, and industrialapparels.

While certain embodiments have been disclosed, other embodiments arealso possible.

In some embodiments, an effective amount of various additives can beincorporated in film 12 or nonwoven substrate 14. Suitable additivesinclude pigments, antistatic agents, antioxidants, ultraviolet lightstabilizers, antiblocking agents, lubricants, processing aids, waxes,coupling agents for fillers, softening agents, thermal stabilizers,tackifiers, polymeric modifiers, hydrophobic compounds, hydrophiliccompounds, anticorrosive agents, and mixtures thereof. In certainembodiments, additives such as polysiloxane fluids and fatty acid amidescan be included to improve processability characteristics.

Pigments of various colors can be added to provide the resultantmultilayer article 10 that is substantially opaque and exhibits uniformcolor. For example, multilayer article 10 can have a sufficient amountof pigments to produce an opacity of at least about 85% (e.g., at leastabout 90%, at least about 95%, at least about 98%, or at least about99%). Suitable pigments include, but are not limited to, antimonytrioxide, azurite, barium borate, barium sulfate, cadmium pigments(e.g., cadmium sulfide), calcium chromate, calcium carbonate, carbonblack, chromium(III) oxide, cobalt pigments (e.g., cobalt(II)aluminate), lead tetroxide, lead(II) chromate, lithopone, orpiment,titanium dioxide, zinc oxide and zinc phosphate. Preferably, the pigmentis titanium dioxide, carbon black, or calcium carbonate. The pigment canbe about 1 percent to about 20 percent (e.g., about 3 percent to about10 percent) of the total weight of film 12 or nonwoven substrate 14.Alternatively, the pigment can be omitted to provide a substantiallytransparent multilayer article.

In some embodiments, certain additives can be used to facilitatemanufacture of multilayer article 10. For example, antistatic agents canbe incorporated into film 12 or nonwoven substrate 14 to facilitateprocessing of these materials. In addition, certain additives can beincorporated in multilayer article 10 for specific end applications. Forexample, anticorrosive additives can be added if multilayer article 10is to be used to package items that are subject to oxidation orcorrosion. As another example, metal powders can be added to providestatic or electrical discharge for sensitive electronic components suchas printed circuit boards.

Each of film 12 and nonwoven substrate 14 can also include a filler. Theterm “filler” can include non-reinforcing fillers, reinforcing fillers,organic fillers, and inorganic fillers. For example, the filler can bean inorganic filler such as talc, silica, clays, solid flame retardants,Kaolin, diatomaceous earth, magnesium carbonate, barium carbonate,magnesium sulfate, calcium sulfate, aluminum hydroxide, zinc oxide,magnesium hydroxide, calcium oxide, magnesium oxide, alumina, mica,glass powder, ferrous hydroxide, zeolite, barium sulfate, or othermineral fillers or mixtures thereof. Other fillers can include acetylsalicylic acid, ion exchange resins, wood pulp, pulp powder, borox,alkaline earth metals, or mixtures thereof. The filler can be added inan amount of up to about 60 weight percent (e.g., from about 2 weightpercent to about 50 weight percent) of film 12 or nonwoven substrate 14.

In some embodiments, the surface of film 12 or nonwoven substrate 14 canbe at least partially treated to promote adhesion. For example, thesurface of film 12 or nonwoven substrate 14 can be corona charged orflame treated to partially oxidize the surface and enhance surfaceadhesion. Without wishing to be bound by theory, it is believed thatmultilayer article 10 having enhanced surface adhesion can enableprinting on its surface using conventional inks. Ink jet receptivecoating can also be added to the surface of multilayer article 10 toallow printing by home or commercial ink jet printers using water basedor solvent based inks.

The following example is illustrative and not intended to be limiting.

EXAMPLE 1

The following two multilayer articles were prepared: (1) TYPAR (i.e., apolypropylene spunbonded nonwoven substrate available from Fiberweb,Inc) having a unit weight of 1.9 ounce per square inch and coated with amicroporous breathable film containing 60 wt % polypropylene, 20 wt %KRATON (i.e., a styrenic block copolymer serving as a compatibilizer)available from Kraton Polymers U.S. LLC (Houston, Tex.), and 20 wt %styrene (i.e., a conventional immiscible polymer), and (2) a multilayerarticle similar to multilayer article (1) except that it contained amicroporous breathable film that included 65 wt % polypropylene, 30 wt %APEL (i.e., an exemplary polycycloolefin copolymer disclosed herein),and 5 wt % low-density polyethylene. Both multilayer articles wereformed by extruding the microporous breathable film onto TYPAR at 480°F. and had total film unit weights of 22 gsm.

Multilayer article (1) and (2) were evaluated for their MVTR and theircapability of forming uniform breathable films. The MVTR was measured byusing ASTM E96-A. The test results are summarized in Table 1 below.

TABLE 1 Sample Uniformity Observation MVTR (Perm) (1) Holes in the filmN/A (2) Uniform film 11.1 after ring rolling

The results showed that, when using a conventional immiscible polymer,the microporous breathable film in multilayer article (1) exhibited pooruniformity (i.e., poor processability) even though it contained as muchas 20 wt % of a compatibilizer. Unexpectedly, when using as much as 30wt % of an exemplary immiscible polymer (i.e., APEL) described in thisdisclosure, multilayer article (2) exhibited superior uniformity in themicroporous breathable film even though no compatibilizer was used inthe film.

Other embodiments are in the claims.

What is claimed is:
 1. A method of making an article, comprising:forming a laminate comprising a nonwoven substrate and a microporousbreathable film supported by the nonwoven substrate, wherein themicroporous breathable film comprises a first polymer and a secondpolymer, the second polymer being immiscible with the first polymer, thefirst polymer comprises a polyolefin, and the second polymer comprises apolycycloolefin, a polymethylpentene, or a copolymer thereof; andstretching the laminate to form the article; wherein the microporousbreathable film is devoid of a pore-forming filler, and wherein thelaminate has a MVTR from 35 g/m²/day to 140 g/m²/day according to ASTME96-A and measured at 23° C. and 50 RH %.
 2. The method of claim 1,wherein forming the laminate comprises extruding the film onto thenonwoven substrate.
 3. The method of claim 1, wherein the laminate isstretched and at an elevated temperature.
 4. The method of claim 3,wherein the elevated temperature is at least about 30° C.
 5. The methodof claim 1, wherein the laminate is stretched in the machine direction.6. The method of claim 1, wherein the laminate is stretched in thecross-machine direction.
 7. The method of claim 1, wherein the laminateis stretched by a method selected from the group consisting of ringrolling, tentering, embossing, creping and button breaking.
 8. Themethod of claim 1, further comprising embossing the laminate prior to orafter stretching the laminate.
 9. The method of claim 1, furthercomprising bonding randomly disposed polymeric fibers to produce thenonwoven substrate prior to forming the laminate.
 10. The method ofclaim 1, wherein the first polymer comprises at most about 99% of atotal weight of the microporous breathable film and an amount of thesecond polymer comprises at least about 1% of the total weight of themicroporous breathable film.
 11. The method of claim 10, wherein thesecond polymer has a polymer backbone similar to that of the firstpolymer such that at least about 5% by weight of the amount of thesecond polymer is blended with the first polymer.
 12. The method ofclaim 10, wherein at least about 30% by weight of the amount of thesecond polymer is blended with the first polymer.
 13. The article ofclaim 10, wherein 5-30% by weight of the amount of the second polymer isblended with the first polymer.
 14. The method of claim 1, wherein thesecond polymer comprises a poly(cycloolefin-co-olefin).
 15. The methodof claim 1, wherein the second polymer comprises apoly(norbornene-co-ethylene) or a copolymer formed from ethylene andnorbornene substituted with a substituent.
 16. The method of claim 1,wherein the first polymer comprises a polyethylene or a polypropylene.